Honestly I can't think of any use for it, other than as a finishing blow (which is so not worth it, vis a vis taking one of the other vicious trophies) or with Earthmother. Using WEYTWUT or WONAFYT with it is actually MP-inefficient; you'll do more damage for less MP just casting two fireballs. Even with Earthmother, you're probably not much better off than you'd be with the Plantation/Clearance trick, especially if you have any of the other fireball boosters. It would be pretty handy if you were fireballing something that already has counter fireball, but I can't think of any situation where you'd actually want to do that (or at least not so much that it would be worth foregoing some other locker item).